The present invention is a vehicle seat assembly with a high tension back frame. Such a back frame is particularly useful in a seat assembly in which a shoulder belt is coupled to the backrest of the seat assembly resulting in the back frame carrying the shoulder loads during a vehicle collision.
Motor vehicles are typically provided with an occupant restraint system comprised of belts which often includes a lap belt and a shoulder belt. These belts restrain an occupant within a vehicle seat assembly during a collision. Most often, the belt restraint system is mounted directly to the vehicle body structure adjacent to the seat assembly. The position of the seat assembly, relative to the vehicle body, is adjustable in at least the fore and aft direction and may be adjustable in other directions as well. When the belt restraint system is mounted to the vehicle body, the seat assembly moves relative to the belt restraint system. Because of the relative movement between the belt restraint system and the seat assembly, it can become inconvenient or uncomfortable for a seat occupant to use the belt restraint system in some positions of the seat assembly. For example, if the vehicle seat is moved to its forward most position, it may be difficult to reach rearward to grasp the belt mounted to the vehicle body behind the seat assembly. Furthermore, in some positions of the seat assembly, the shoulder belt may rub across the occupant's neck, creating discomfort.
Accordingly, it is becoming more common to mount the belt restraint system directly to the seat assembly so that the restraint system moves with the seat assembly during adjustment. However, with the attachment of the restraint system to the seat assembly, it is necessary to increase the load carrying capability of the seat assembly to accommodate the restraint system loads. The result of increasing the seat assembly strength is often an increase in the seat assembly weight. This weight increase is contrary to the desire of vehicle manufacturers to reduce the weight of motor vehicles and thus improve fuel efficiency.
Accordingly, it is an object of the present invention to provide a seat assembly with increased load carrying capability to accommodate the restraint system loads while minimizing the increase in the seat weight.